As many of you may know...The 85 L II is a special lens...but not the closest focusing lens out there. I find that, sometimes to get in tight I am using a (3rd-party) 12mm extension tube...but I am having some issues with this set-up on my 5DIII... (BTW my copy of the lens is spot-on with AF accuracy,i.e. AF micro adjustment is zero.).

1. When I use my 3rd party extension tube...I find that I have to set the AF Micro Adjustment to +20. Does anyone using this set-up with the Canon 12mm Extension Tube II have this much variation in AF?2. When I use my set-up with the 3rd-party tube, in the AF Micro Adjustment Menu my 5DIII recognizes my set-up as "only" the 85mm lens (not lens plus tube)...and therefore each time I use this set-up I have to manually enter the AF Micro Adjustment and then set the MA back to zero or it will throw off my AF the next time I use the 85mm without the ext tube. My 2nd question is: If I use the 85mm with the Canon 12mm Extension Tube II does the AF Micro adjustment menu on my 5D III recognize this set-up as 85mm PLUS 12mm Ext. Tube and keep it separate from the AF Micro Adjustment for the 85mm by itself? (i.e. does the AF Micro Adjustment Menu treat this situation the same as it does when I use a Canon Tele Extender on a Canon Lens?)Thanks.